To clarify he was an Iranian historian who took a keen interest in Islamic studies. He always claimed this, but I was curious what some other people thought about his idea.
Edit: I meant the niqab, not the hijab, thank you for pointing this out.
Do you mean the hijab which is a head scarf or a full body covering like the burka/face covering like the niqab? With the hijab, there is no way it would hide a mistress, it would only hide her hair.